as you signed the leasing contract with your dealer, the car price was already set on the contract. I don't think you could make them get less profits when you purchase that car. maybe you could, but not much. If I were you, I will return the car as the leasing term is expired. I will then purchase/finance another car you like.
remember!! leasing is not for every one. it is good for some people who like to change car every few years in order to trouble free or for business use (register the car under the company name).
if you are not both types, then buy or finace one. that is the only way you save your money.